Irrigated ablation catheter assembly having a flow member to create parallel external flow

ABSTRACT

The invention relates to irrigated ablation catheter assemblies and methods of facilitating parallel irrigation fluid flow along irrigated assemblies. An irrigated catheter assembly according to an embodiment includes a catheter, an irrigated ablation electrode assembly, and a flow member. The catheter includes a catheter shaft having a fluid lumen. The irrigated ablation electrode assembly includes a proximal portion having at least one irrigation passageway and a distal portion. The proximal portion of the electrode assembly may include a proximal member and the distal portion of the electrode assembly may include a distal member which is connected to the proximal member. The proximal end of the flow member is coupled or connected to the catheter shaft and the distal end of the flow member is disposed about the proximal portion of the electrode assembly. Fluid flows through the irrigated electrode assembly and is guided, at least in part, along the outer surface of the proximal portion by the flow member towards the distal portion along the outer surface of the distal portion substantially parallel with the longitudinal axis of the electrode assembly.

BACKGROUND OF THE INVENTION

a. Field of the Invention

The present invention generally relates to ablation electrodes and/orcatheter assemblies having a mechanism for irrigating targeted areas.The present invention further relates to irrigated catheter assembliesthat allow for a parallel irrigation flow path through the incorporationof a flow guide or member on the outer surface of the electrodeassembly.

b. Background Art

Electrophysiology catheters have been used for an ever-growing number ofprocedures. For example, catheters have been used for diagnostic,therapeutic, and ablative procedures, to name just a few examples.Typically, a catheter is manipulated through a patient's vasculature toan intended site, for example, a site within the patient's heart, andcarries one or more electrodes, which may be used for ablation,diagnosis, or other treatments.

There are a number of methods used for ablation of desired areasincluding, for example, radiofrequency (RF) ablation. RF ablation isaccomplished by transmission of radiofrequency energy to a desiredtarget area through an electrode assembly to ablate tissue at a targetsite. Because RF ablation may generate significant heat, which if notcontrolled can result in undesired or excessive tissue damage, such assteam pop, tissue charring, and the like, it is commonly desirable toinclude a mechanism to irrigate the target area and the device withbiocompatible fluids, such as a saline solution. The use of irrigatedablation catheters can also prevent the formation of soft thrombusand/or blood coagulation.

Typically, there are two general classes of irrigated electrodecatheters, i.e., open irrigation catheters and closed irrigationcatheters. Closed ablation catheters usually circulate a cooling fluidwithin the inner cavity of the electrode. Open ablation catheterstypically deliver the cooling fluid through open outlets or openings onor about an outer surface of the electrode. Open ablation cathetersoften use the inner cavity of the electrode, or distal member, as amanifold to distribute saline solution, or other irrigation fluids knownto those skilled in the art, to one or more passageways that lead toopenings/outlets provided on the surface of the electrode. The salinethus flows directly through the outlets of the passageways onto or aboutthe distal electrode member. This direct flow of fluid through theelectrode tip lowers the temperature of the tip during operation,rendering accurate monitoring and control of the ablative process moredifficult. Accordingly, it is desirable to have a method that allows forcooling of the electrode while providing accurate monitoring and controlof the ablative process.

Even for electrode assemblies that are designed with the incorporationof irrigation passageways, if an electrode has a longer length (i.e.,for example, over 3 mm), there may be an increased likelihood ofdeveloping thrombus caused by protein aggregation and blood coagulationat the tip of the electrode since the standard angled irrigation flow isdirected away from the electrode tip and does not reach the longer tipportion or the more distal regions of the electrode due to it length.Moreover, as the length of the electrode increases, the angled fluidpassageways provided by an electrode assembly, may be less effective iftoo much fluid is directed away from the electrode instead of along thebody of the electrode to effectively cool the electrode and provideadequate irrigation to prevent the development of thrombus at the distalarea of the electrode. Further, for some applications, open flushirrigated ablation catheters with parallel flow may improve the safetyof RF catheter ablation by preventing or mitigating protein aggregationand blood coagulation on the surface of the electrode.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to ablation electrode assemblies. Thepresent invention further relates to an irrigated ablation electrodeassembly that includes a flow guide or member for creating parallelirrigation flow along the distal member, i.e. ablation electrode, of theelectrode assembly.

The present invention also relates to an irrigated ablation catheterassembly. The irrigated catheter assembly includes a catheter, anirrigated ablation electrode assembly, and a flow member. The catheterincludes a catheter shaft having a fluid lumen. The irrigated ablationelectrode assembly includes a proximal member and a distal member. Theproximal member of the electrode assembly further includes a bodyportion including an outer surface, an inner cavity within the outerbody portion, and at least one passageway that extends from the innercavity to the outer surface of the body portion. The distal member ofthe electrode assembly further includes a distal end. The flow member ofthe catheter assembly has a body that includes a proximal end and adistal end. The body of the flow member may be tubular. The proximal endof the flow member is coupled or connected to the catheter shaft and thedistal member of the flow member is disposed about the proximal memberof the electrode assembly. Accordingly, fluid flows through theirrigated electrode assembly and is guided along the outer surface ofthe proximal member by the flow member towards the distal member alongthe outer surface of the distal member substantially parallel with thelongitudinal axis of the electrode assembly.

The present invention further provides a method for creating parallelfluid flow along an irrigated electrode assembly. The method includespositioning a fluid member having a body including a proximal end and adistal end about a catheter shaft and proximal member of an irrigatedelectrode assembly. The body of the flow member may be tubular. Theproximal end of the tubular body is connected to the catheter shaft andthe proximal end of the body is disposed about an outer surface of theproximal member of the irrigated electrode assembly. The method furtherincludes delivering a fluid to an inner cavity of the proximal memberand to at least one passageway that extends from the inner cavity of theproximal member to the outer surface of the proximal member. The fluidflows between the outer surface of the proximal member and the fluidguide towards a distal member of the irrigated electrode assemblysubstantially in parallel with the longitudinal axis of the electrodeassembly.

The present invention further relates to an ablation catheter systemincluding an irrigated ablation electrode assembly connected to acatheter shaft having a flow member connected to or coupled with thecatheter shaft and the electrode assembly, therein forming an irrigatedcatheter assembly connected to an energy source and a fluid source.

The foregoing and other aspects, features, details, utilities, andadvantages of the present invention will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an irrigated ablation catheterassembly in accordance with an embodiment of the present invention;

FIG. 2 is an isometric view of a flow member in accordance with anembodiment of the present invention;

FIG. 3A is a cross-sectional view of an irrigated ablation catheterassembly in accordance with an embodiment of the present invention;

FIG. 3B is an illustrative cross-sectional view of the irrigatedablation catheter assembly as shown in FIG. 2A;

FIG. 4 is an isometric view of a flow member in accordance with anembodiment of the present invention;

FIG. 5A is a cross-sectional view of an irrigated ablation catheterassembly in accordance with an embodiment of the present invention;

FIG. 5B is an illustrative cross-sectional view of the irrigatedablation catheter assembly as shown in FIG. 3A;

FIG. 6 is a cross-sectional view of an irrigated ablation catheterassembly in accordance with an embodiment of the present invention; and

FIG. 7 is a end view of a flow member in accordance with an embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In general, the instant invention relates to irrigated ablationelectrode assemblies and methods of using the irrigated ablationelectrode assemblies in connection with catheter assemblies. Forpurposes of this description, similar aspects among the variousembodiments described herein will be referred to by the same referencenumber. As will be appreciated, however, the structure of the variousaspects may differ among various embodiments.

As generally shown in the embodiment illustrated in FIG. 1, the ablationelectrode assembly 10 may comprise part of an irrigated ablationcatheter assembly 12. Embodiment of the invention describe RF ablationirrigated catheter assemblies; however, the invention may be equallycompatible with and applicable to a number of other types of ablationelectrodes and catheter assemblies where the temperature of the deviceand the targeted tissue area may be factors associated with atherapeutic procedure. FIGS. 2 through 7, discussed in more detail,illustrate irrigated catheter assemblies 12 and related componentsaccording to alternate embodiments of the present invention.

FIG. 1 is an isometric view of an irrigated ablation electrode assembly10 connected to a catheter shaft 14 as part of irrigated ablationcatheter assembly 12 in accordance with an embodiment of the invention.Catheter assembly 12 includes at least one fluid delivery tube 16 forsupplying fluid to electrode assembly 10. Fluid delivery tube 16 may bedisposed within a lumen 19 included within catheter shaft 14. Lumen 19may be a passageway for receiving fluid delivery tube 16, whichtransport fluid, such as a saline solution, or alternatively fluid maybe provided directly through lumen 19 for supplying the irrigatedelectrode assembly 10. FIG. 1 generally illustrates an irrigatedablation catheter assembly 12 of the type that may be provided by and/orused in connection with the present invention.

As generally illustrated in FIG. 1, electrode assembly 10 may include aproximal member 18 (also referred to as an irrigation member ormanifold) and a distal member 20 (also referred to as an ablationelectrode member). Proximal member 18 and distal member 20 can beconfigured for connection together. The orientation of members 18, 20are generally such that distal member 20, which provides an ablationelectrode or an ablative surface, may be provided or situated at orabout the distal end of assembly 10. Proximal member 18 may also bereferred to as a “proximal portion.” Similarly, distal member 20 mayalso be referred to as a “distal portion.” For some embodiments,electrode assembly 10 may be designed and configured to comprise asingle unitary electrode assembly 10 that includes a proximal portionand a distal portion. In other embodiments, electrode assembly maycomprise a multi-component electrode assembly 10 havingseparately-formed proximal and distal portions.

Proximal member 18 (i.e., irrigation member) may be provided or locatedat the proximal end of electrode assembly 10. However, for someembodiments, the orientation could be reversed. Proximal member 18includes a body portion 22 having an outer surface 24. Proximal member18 further includes at least one fluid or irrigation passageway 26 (alsoreferred to as proximal passageway 26) that extends from an inner cavity28, which is disposed within body portion 22, to an orifice or outletprovided by outer surface 24 of proximal member 18. In an embodiment,proximal passageway 26 is separated from and does not come in contactwith distal member 20. Inner cavity 28 is generally configured for fluidcommunication with fluid delivery tube 16. Fluid delivery tube 16 may besecurely provided in fluid communication with inner cavity 28 throughthe coupling to or connection with a seal member 17, which may forexample be provided about tube 16 and inserted within inner cavity 28.

Proximal member 18 may include a plurality of passageways 26 that areconfigured to provide for the flow of fluid through proximal member 18to outer surface 24 of proximal member 18, and moreover to electrodeassembly 10. In an embodiment, inner cavity 28 may serve or act as amanifold or distributor for transporting and/or distributing fluidthroughout portions of electrode assembly 10. For example, proximalmember 18 may be configured to receive a fluid delivery tube 16 carriedwithin at least a portion of catheter shaft 14. Proximal member 18 mayserve as a manifold or distributor of fluid to electrode assembly 10through passageways 26. Proximal passageways 26 may extend from innercavity 28 radially outward at an acute angle toward outer surface 24 ofproximal member 18. In an embodiment, a plurality of passageways 26 aresubstantially equally distributed around the circumference of proximalmember 18 to provide substantially equal distribution of fluid to thetargeted tissue area and/or the outside of electrode assembly 10. Ifdesired, electrode assembly 10 may be configured to provide a single,annular passageway 26, or a number of individual passageways 26 that maybe equally distributed around at least a portion of the outer surface 24of the proximal member 18. Passageways 26 extend to an orifice or outletprovided by outer surface 24. Moreover, the passageways 26 may begenerally tubular and may have a substantially constant diameter alongthe length of the passageway. Alternate configurations of passageways 26having various diameters along all or portions of the length of thepassageways may also be provided.

As shown in FIG. 1, irrigation passageways 26 may be directed towards orextend towards distal member 20 of electrode assembly 10. In anembodiment, passageways 26 extend from the inner cavity 28 of proximalmember 18 towards distal member 20 such that a line extendingsubstantially through the center of the passageway 26 forms an acuteangle with a longitudinal axis (l) of electrode assembly 10. In anembodiment, irrigation passageways 26 may be directed towards or extendtowards distal member 20 at an angle (Θ) equal or less than 90 degreesfrom the central longitudinal axis of proximal member 18. In anembodiment, passageway 26 extends at an angle (Θ) between about 45 toabout 90 degrees. Alternate positions and angles of the passageway(s) 26may be provided in alternate embodiments of electrode assembly 10.

Based on the angled position of irrigation passageways 26, e.g., asgenerally illustrated in FIG. 1, the flow of fluid exiting proximalmember 18 may have limited contact with distal member 20. In particular,as distal member 20 is increased in length, such as ranging fromapproximately 3 millimeters to 8 millimeters compared to a 2.5millimeter distal member, the flow of irrigation fluid, as generallydepicted by arrows (F), may be directed away from distal member 20 andlimited contact may occur between the irrigation fluid and distal member20. Accordingly, it can be desirable to provide a more parallel fluidflow, wherein the fluid (F) has a more substantial flow along the outersurface 30 of distal member 20.

Distal member 20, is generally comprised of an electrically, andpotentially thermally, conductive material known to those of ordinaryskill in the art for delivery of ablative energy to target tissue areas,and may therein provide an ablation electrode. Examples of electricallyconductive material include gold, platinum, iridium, palladium,stainless steel, and various mixtures and combinations thereof. In anembodiment, the distal member may provide a distal end 32 that may berounded (e.g., partially spherical or hemispherical), although otherconfigurations may be used. Distal member 20 may further include athermal sensor 38, which may be disposed within a thermal cavity 39.Thermal sensor 38 may be disposed along the central longitudinal axis ofdistal member 20. Such a positioning of thermal sensor 38 may furtherenhance the temperature sensing properties or capabilities of electrodeassembly 10. Thermal sensor 38 can be any mechanism known to one ofskill in the art, including for example, thermocouples or thermistors.The temperature sensor 38 may further be substantially surrounded, or atleast partially encapsulated, by a thermally conductive and electricallynon-conductive material. This thermally conductive and electricallynon-conductive material can serve to hold temperature sensor 38 in placewithin distal member 20 and provide improved heat exchange betweentemperature sensor 38 and distal member 20. This material may becomprised of a number of materials known to one of ordinary skill in theart, including for example, thermally conductive resins, epoxies, orpotting compounds.

Proximal member 18 is comprised of a thermally nonconductive or reduced(i.e. poor) thermally conductive material that serves to insulate thefluid from the remaining portions of electrode assembly 10, for example,distal member 20. Moreover, proximal member 18 may comprise anelectrically nonconductive material. Comparatively, proximal member 18may have lower thermal conductivity than distal member 20. In anembodiment, proximal member 18 may comprise a reduced thermallyconductive polymer. A reduced thermally conductive material is one withphysical attributes that decrease heat transfer by about 10% or more,provided that the remaining structural components are selected with theappropriate characteristics and sensitivities to maintain adequatemonitoring and control of the process. Moreover, a reduced thermallyconductive material may include polyether ether ketone (“PEEK”). Furtherexamples of reduced thermally conductive materials that may be useful inconjunction with the present invention include, but are not limited to,high-density polytheylene, polyimides, polyaryletherketones,polyetheretherketones, polyurethane, polypropylene, orientedpolypropylene, polyethylene, crystallized polyethylene terephthalate,polyethylene terephthalate, polyester, polyetherimide, acetyl, ceramics,and various combinations thereof. Moreover, for some embodiments,proximal member 18 may be substantially less thermally conductive thandistal member 20. As a result, the irrigation fluid flowing throughproximal member 18 may have very little thermal effect on distal member20 due to the poor thermal conductivity of proximal member 18 (e.g. lessthan 5% effect), and preferably may have nearly 0% effect.

The proximal member 18 may further be configured to include a couplingportion 34 that extends into inner cavity 36 of distal member 20.Proximal member 18 may be generally cylindrical in shape. Moreover, forsome embodiments, distal member 20 of ablation electrode assembly 10 mayhave a generally cylindrical shape terminating in a hemispherical distalend 32. The cylindrical shape of proximal member 18 and distal member 20may be substantially similar to one another and generally have the sameoverall diameter, which can provide or create a flush or substantiallysmooth outer body or profile for electrode assembly 10. Distal member 20may be configured to accept portion 34 of proximal member 18 forattachment thereto. The distal member 20 may be connected by variousknown mechanisms, including adhesives, press-fit configurations,snap-fit configurations, threaded configurations, or various othermechanism known to persons of ordinary skill in the art.

To help guide or direct the flow of fluid about and along the outersurface 30 of distal member 20 of electrode assembly 10, a flow member40, for example as generally illustrated in FIG. 2, may be coupled orconnected to catheter assembly 12. Flow member 40 may be generallycylindrical in shape. In an embodiment, flow member 40 may include abody 42 that may partially surround the outer surface 24 of proximalmember 18. In an embodiment, flow member 40, as seen in FIG. 2, mayinclude a tubular body 42 having a proximal end 44 and a distal end 46.Tubular body 42 may include a flow member lumen 48 that receives atleast a portion of catheter assembly 12, for example as generallyillustrated in FIGS. 3A and 3B. In an embodiment, the body 42 associatedwith flow member 40 may have a wall thickness of approximately 0.001inches to approximately 0.005 inches. In an embodiment, flow member 40may be comprised of a polymer or polymeric material, for example,tubing, and may include various types of polymer tubing known by thoseof ordinary skill in the art that are suitable for the intendedapplication and treatment environment. In an embodiment, flow member 40may be comprised of polymer tubing, selected from PEBAX®, polyurethaneand mixtures thereof. Further, in an embodiment, flow member 40 may havea substantially constant inner diameter (D). Moreover, in an embodiment,the inner diameter of flow member 40 may be slightly greater than theouter diameter of catheter assembly 12, such that catheter assembly 12may be attached within flow member 40 and positioned such that flowmember 40 is securely attached to catheter assembly 12 at a desiredposition or location. In another embodiment, flow member 40 may beelastic, having adequate flexibility, to therein permit flow member 40to stretch to allow fluid flow towards distal member 20. Accordingly,flow member 40 may be comprised of a substantially elastic material,such as those recognized by persons of ordinary skill in the art.

As generally illustrated in FIG. 3A, flow member 40 may be securelyattached in connection with catheter assembly 12, including aspreviously described. In an embodiment, proximal end 44 of flow member40 may be securely coupled or connected to catheter shaft 14 of catheterassembly 12. Various connections, coupling mechanisms, or means forcoupling may be used for sufficiently securing proximal end 44 tocatheter shaft 14. Such mechanisms include, but are not limited to,adhesives, bonding (e.g., through heating), pressure, mechanical force,or other mechanism known by those of ordinary skill in the art. Asillustrated in FIG. 3B, once fluid is delivered through fluid deliverytube 16 into inner cavity 28 and through passageways 26 of proximalmember 18, the fluid may exit passageways 26 and be guided by flowmember 40 towards distal member 20 about and along outer surface 30.Accordingly, body 42 directs the fluid flow in a direction substantiallyparallel with outer surface 30 of distal member 20. In an embodiment,flow member 40 may further be provided to prevent the backflow of bloodinto catheter assembly 12.

In an embodiment, for example as generally shown in FIG. 4, flow member40′ may include a preformed body 50 having an expanded portion 52 thatis provided between proximal end 44 and distal end 46. Expanded portion52 may have a inner diameter (D1) that is perceptively, or evensubstantially, greater than the inner diameter (D) of proximal end 44and distal end 46 of flow member 40′. As further generally illustratedin FIGS. 5A and 5B, upon the insertion of catheter shaft 14 havingelectrode assembly 10 within flow member lumen 48 of flow member 40′, acircumferential space 54 may generally be provided between outer surface24 of proximal member 18 and preformed body 50 of flow member 40′.Expanded portion 52 enables evenly distributed fluid flow between outersurface 24 of proximal member 18 and preformed body 50 of flow member40′. Accordingly, flow member 40′ may be more readily displaced upon theflow of fluid from passageways 26 and allow for the parallel flow offluid along outer surface 30 of distal member 20. In an embodiment,distal end 46 of flow member 40′ may be elastic and can move radiallytowards and away from proximal member 18 upon the flow of fluid throughdistal end 46. Accordingly, distal end 46 of flow members 40 and 40′ maybe elastic and can move radially towards and away from electrodeassembly 10 to facilitate parallel fluid flow along electrode assembly10 towards distal member 20.

FIG. 6 further illustrates an alternate embodiment, wherein flow member40″ includes a support member 56 disposed between flow member 40″ andouter surface 24 of proximal member 18 as well as catheter shaft 14.Support member 56 may be positioned relative to proximal member 18 suchthat support member 52 is disposed proximally to passageways 26.Circumferential space 58 is provided between outer surface 24 ofproximal member 18 and distal end 46 of flow member 40″. Proximal end 44of flow member 40″ has a diameter less than distal end 46 of flow member40″. In an embodiment, the diameter of distal end 46 may besubstantially equal to the diameter of proximal end 44 plus thethickness of support member 56. The design of flow members 40, 40′ and40″ may vary depending on the types of materials used and/or variousstructural alternations made during the manufacturing process intendedto facilitate parallel irrigation flow along electrode assembly 10.

FIG. 7 illustrates an additional embodiment of the present invention,wherein flow member 40′″ further includes a plurality of axialpassageways 60 that are provided along the inner surface 62 of body 64of flow member 40′″. Flow member 40′″ further includes a flow memberlumen 48 for receiving catheter shaft 14 and electrode assembly 10.Axial passageways 60 may be equally disposed circumferentially about allor a portion of the inner surface 62 of body 64. Moreover, axialpassageways 60 may extend along a portion of inner surface 62 to distalend 46 of flow member 40′″. Axial passageways 60 provide fluid channelsfor the fluid to flow through to further allow for parallel irrigationfluid flow about and along electrode assembly 10, including in parallelwith distal member 20.

Although a number of embodiments of this invention have been describedabove with a certain degree of particularity, those skilled in the artcould make numerous alterations to the disclosed embodiments withoutdeparting from the spirit or scope of this invention. Other embodimentsand uses of the devices and method of the present invention will beapparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed therein.

All directional references (e.g., upper, lower, upward, downward, left,right, leftward, rightward, top, bottom, above, below, vertical,horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentinvention, and do not create limitations, particularly as to theposition, orientation, or use of the invention. Joinder references(e.g., attached, coupled, connected, and the like) are to be construedbroadly and may include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relation to each other. It is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative only and not limiting.Changes in detail or structure may be made without departing from thespirit of the invention as defined in the appended claims.

1. An irrigated ablation catheter assembly comprising: a catheterincluding a catheter shaft having a lumen; an irrigated ablationelectrode assembly including a proximal portion and a distal portiondisposed distally of the proximal portion, the proximal portion having abody portion including an outer surface, an inner cavity within the bodyportion, and at least one passageway that extends from the inner cavityto the outer surface of the body portion; and a flow member having abody including a proximal end and a distal end, wherein the proximal endof the flow member is coupled or connected to the catheter shaft and thedistal end of the flow member is disposed about the proximal portion ofthe electrode assembly so as to overlay an outlet for the passageway,further wherein the body of the flow member includes a plurality ofaxial passageways disposed within an inner surface of the body, thepassageways extending within a portion of the body to the distal end ofthe body.
 2. The catheter assembly of claim 1, wherein the body of theflow member is substantially tubular.
 3. The catheter assembly of claim1, wherein the axial passageways are evenly distributedcircumferentially about the inner surface of the body of the flowmember.
 4. The catheter assembly of claim 1, wherein the flow member iscomprised of a polymeric material.
 5. The catheter assembly of claim 4,wherein the polymeric material is selected from the group consisting ofpolyurethane, a second polymeric material, and mixtures thereof.
 6. Thecatheter assembly of claim 4, wherein the flow member is made of anelastic material.
 7. The catheter assembly of claim 1, wherein theproximal portion includes a proximal member and the distal portionincludes a distal member, which is connected to the proximal member, thedistal member being electrically conductive.
 8. The catheter assembly ofclaim 7, wherein the proximal member is electrically nonconductive. 9.The catheter assembly of claim 7, wherein the proximal member has alower thermal conductivity than the distal member.
 10. The catheterassembly of claim 1, wherein the distal portion is approximately 3millimeters to approximately 8 millimeters in length.
 11. The catheterassembly of claim 1, wherein the proximal portion has a lower thermalconductivity than the distal portion.
 12. The catheter assembly of claim1, wherein the proximal portion comprises an electrically nonconductivematerial.
 13. The catheter assembly of claim 1, wherein the proximalportion comprises a plurality of passageways disposed circumferentiallyabout and extending to the outer surface of the body portion.
 14. Thecatheter assembly of claim 13, wherein the passageways extend from theinner cavity of the proximal portion towards the distal portion, suchthat a line extending substantially through the center of one of thepassageways forms an acute angle with a longitudinal axis of theelectrode assembly.
 15. The catheter assembly of claim 1, wherein athermal sensor is disposed within the distal portion.
 16. The catheterassembly of claim 1, wherein the distal end of the flow member ismovable radially away from the proximal portion, thereby allowing fluidto flow between the flow member and the proximal portion towards thedistal portion of the electrode assembly.
 17. The catheter assembly ofclaim 1, wherein the distal portion of the electrode assembly has adistal end with a rounded outer surface.
 18. An irrigated ablationelectrode assembly comprising: a proximal portion and a distal portionwhich is disposed distally of the proximal portion; the proximal portionhaving a body portion including an outer surface, an inner cavity withinthe body portion, and at least one passageway that extends from theinner cavity to at least one orifice at the outer surface of the bodyportion in a direction generally toward the distal portion at an acuteangle relative to a longitudinal axis of the electrode assembly; thedistal portion having a distal end and an outer surface; means forguiding a fluid flowing out of the at least one orifice at the outersurface of the body portion to flow along at least a portion of theouter surface of the distal portion in a direction generally parallel tothe outer surface portion toward the distal end; and a support memberconfigured to be disposed between the means for guiding a fluid and acatheter shaft portion disposed proximate the proximal portion so as toprovide a circumferential space between a portion of the means forguiding a fluid and a portion of the proximal portion.
 19. The electrodeassembly of claim 18, wherein the distal end of the distal portion has arounded outer surface.
 20. The electrode assembly of claim 18, whereinthe proximal portion includes a proximal member and the distal portionincludes a distal member which is connected to the proximal member, thedistal member being electrically conductive.
 21. The electrode assemblyof claim 20, wherein the proximal member is electrically nonconductive.22. The electrode assembly of claim 20, wherein the proximal member hasa lower thermal conductivity than the distal member.
 23. The electrodeassembly of claim 18, wherein the outer surface portion of the distalportion is generally parallel to the longitudinal axis of the electrodeassembly.
 24. The electrode assembly of claim 18, wherein the outersurface of the body portion is generally parallel to the outer surfaceportion of the distal portion.
 25. A method for facilitating parallelfluid flow along an irrigated electrode assembly, the method comprising:providing a flow member having a body including a proximal end and adistal end, a catheter shaft, and an irrigated electrode assembly havinga proximal portion and a distal portion, wherein the proximal end of thebody is connected to the catheter shaft and the distal end of the bodyis disposed about an outer surface of the proximal portion of theirrigated electrode assembly, further wherein the body of the flowmember includes an expanded portion disposed between the proximal endand the distal end, the expanded portion having a greater inner diameterthan the inner diameter of adjacent portions of the proximal end anddistal end; delivering fluid to an inner cavity of the proximal portionof the electrode assembly and to at least one passageway that extendsfrom the inner cavity of the proximal portion to the outer surface ofthe proximal portion, wherein the fluid flows between the outer surfaceof the proximal portion and the flow member towards the distal portionof the irrigated electrode assembly substantially in parallel with alongitudinal axis of the electrode assembly.
 26. The method of claim 25,wherein the body of the flow member is substantially tubular.